Generally, within the field of manufacture and assembly of circuit boards, electronic components are fed to a component mounting machine for mechanically and/or electrically mounting of the components onto a circuit board. These surface mounted components are often delivered spaced apart along the length of a component tape, which consists of a lower carrier tape provided with compartments, one for each component, and an upper cover or cover tape or protective tape. After the positioning of the electronic components in the corresponding compartments, the cover tape is attached to the carrier tape, for instance by providing either the cover tape or the carrier tape with adhesive areas or by fusing the cover tape to the carrier tape, and the component tape is wound on a component reel. After having wound the component tape on a component reel, the reel is transferred to a component mounting machine, which feeds a component to a certain predetermined picking position where it can be picked, or collected, by a pick-up head.
WO 86/00778 shows a cassette magazine for a component mounting machine using the above described method. The main steps are as follows: introducing the free end of the component tape into a feeding mechanism, provided in the machine or in the magazine, such that feeding pins engage corresponding holes provided in the component tape. Separating, by hand, the end of the cover tape from the end of the carrier tape for a distance sufficient to attach the cover tape to a cover tape handling means. Bringing the cover tape end past a stripping edge which is combined with a plate or a locking mechanism that secures the carrier tape. Lowering the locking mechanism over the carrier tape for holding the carrier tape against the feeding mechanism. Bringing, by hand, the end of the cover tape, and attaching it, to the cover tape handling means; and stretching the cover tape, e.g. by manipulating the cover tape handling means.
Prior to the picking of the components, each component has to be exposed so as to make it available for picking. This is achieved by removing the cover tape from the carrier tape. The cover tape is then fed by separate cover tape handling means in order for the cover tape not to disturb the picking of components. Generally, the cover tape handling means comprises a winding hub on which the cover tape is wound. Additionally, when unloading the component tape from the component mounting machine, or the tape magazine, the winding hub has to be cleared of the cover tape.
A considerable length of the end of the cover tape has to be separated from the end of the carrier tape in order to bring the cover tape end to a cover tape handling means. Thus, the first decimeters of a new carrier tape are not provided with components. Otherwise, numerous components would be wasted during loading. However, when reloading a tape reel that has already been partly used, the tape is provided with components throughout, and consequently a large number of components might be wasted.
The most conventional way of exposing the components in a broad carrier tape, i.e. wider than 8 mm, is to use the method described above. The width of the carrier tapes ranges from 8 to 200 mm, where a width of 8, 12 or 16 mm is the most conventional. The properties of different carrier tapes and covers are well known, and do not differ much between different manufactures, as there is a US standard EIA-481 regulating the basics of component tapes. For example, the standard regulates the peeling force of the component tape, i.e. the force needed to separate the cover from the carrier tape. From this value conclusions can be drawn regarding the elasticity of the cover.
Component tapes having a narrow width, such as 8 mm, may be handled in a different way, described for example in WO 00/38491, where a tape guide is used, which can be loaded with the component tape away from the machine, and which thereafter can be inserted into said machine. When the tape guide is loaded by for example an operator, the component tape is first inserted between two opposing elongated walls of the tape guide. The tape is then manually fed towards a plough mounted on the tape guide, and when the component tape reaches the plough, the operator makes sure that the tip of the plough is inserted between the carrier tape and the cover. Moreover, the plough is further arranged such that when the operator manually continues to feed the component tape past the plough, the plough detaches one of the rim portions of the cover, which are attached to the component tape, but leaves the other rim portion still attached, and as the cover tape is fed further into the tape guide, the cover is raised to an upright position. In a further development of the tape guide, the cover is raised to an upright position by a plough.
In this context the term upright is referring to a direction, which is substantially perpendicular to the plane of the carrier tape, or which is turned further outwards, away from the picking position, thus forming an angle with the plane of the carrier tape of at least about 60 degrees. Here, the plane of the carrier tape is substantially parallel to the plane of the cover, as long as the cover is attached to the carrier tape.
The operator continues to feed the component tape along the tape guide, until the tape has reached a position, where feeding means in the component mounting machine can engage with the component tape, when the tape guide is loaded in the machine.
After the component tape, in the above described way, has been loaded into the tape guide, the tape guide, in turn, is loaded into the component mounting machine, such that a picking head in said machine can pick components from a picking position on the tape guide. The picking position is a position along the tape guide where the cover of the loaded component tape has been opened such that the components are unblocked.
As stated above, this type of tape guide is used for narrow tapes. When using wider tapes, for example 12 or 16 mm broad, raising the cover to an upright position can involve substantial drawbacks, due to the fact that a wide cover raised to an upright position requires a substantial amount of free space above the tape guide. If several tape guides are arranged side by side, the picking head is forced to pass higher above the guides, requiring an increased vertical distance to travel for the picking of components, and thus the time efficiency of the entire manufacturing process is decreased.
An alternative to raising the cover to an upright position, is to raise the cover completely to the side, i.e. turning the loosened part of the cover about 180 degrees, so that it extends beside the component tape. Although this method solves the above problem, it is not a true solution but merely a way of forwarding the problem to another area. Instead of requiring free space above the tape guides, the space is now needed to the side of each tape guide. When the cover is turned completely to the side, the tape guides have to be arranged further apart, so that one cover in one tape guide does not interfere with the neighboring guide.
An early attempt to solve the above problems is described in document U.S. Pat. No. 4,820,369. Here, a guide shoe is provided with tunnel shaped guide means, for causing a loosened portion of the cover tape to curve outwards, upwards and to the side of the picking position, by letting it run inside the guide means, such that at the picking position the loosened cover will be arranged almost in a spiral shaped fashion.
As reliability and efficiency are of great importance within the field of manufacture and assemble of circuit boards, the cover of the component tape simply can not be allowed to obstruct the picking process, or the feeding of the component tape, not even occasionally. If, for instance, the cover would get stuck under the plough in a tape guide, or if the cover would interfere with the picking position, a vast amount of irretrievable time is lost, while the problem is corrected and the component tape is reloaded into the tape guide, and hence the margins of the manufacturing process are reduced. Consequently, when using the tape guide for removing the cover in order to expose components one must make sure that the free rim portion of the cover is well away from the plough and the picking position.